Telegraph code recorder



Dec. 18, 1945. E, BEsTE 2,391,082

TELEGRAPH CODE RECORDER Filed Feb. 11, 1944 W 2/5 Z INVENTOR.

Patented Dec. 18, 1945 2,391,082 TELEGRAPH coon anconmm Harold Edward Beste, East Rutherford, N. J., as-

signor to Allen B. Du Mont Laboratories, Inc., Passaic, N. .L, a corporation of Delaware Application February 11, 1944,8erlal No. 521,901

' 5 Claims. (or 178-811) This invention relates to a device by means of which telegraph code signals are received in such a way that they can be observed visually. In carrying out the invention, received telegraph signals are caused to turn on and deflect the beam or ray of a cathode ray tube to different extents in accordance with the reception of dots and dashes so that traces of different lengths appear on the screen corresponding to the dots and dashes and can be easily observed and the message thereby read.

The received dot and dash signals which consist of high frequency oscillations are converted into direct current signals which deflect the beam and at the same time these dots and dashes are utilized to turn on the beam at the proper times so that the different signals canbe read visibly and distinguished from each other. At the same time the danger of burning the screen of the cathode ray tube is obviated.

The invention may be understood from the description in connection with the accompanying drawing which is a diagram of connections showing an illustrative embodiment of the invention.

In the drawing, reference character I indicates the primary of a transformer to which the output of the usual telegraph code receiver, indicated at a and b as a dash and dot, respectively, is applied. The ends of the secondary 2, 2' are connected to plates of triodes 3 and 4 and these secondaries are tuned by capacitors 5 and 6 to the frequency of the signals a and b which may, for example, be 5 kc. The center point of the secondaries 2, 2' and a point between capacitors 5, G'are connected to a source of negative potential, say 250 volts as indicated at l9.

The signals a and b produce negative direct current signals and d which are the outputs of triodes 3 and 4. These signals are filtered by the RC filter 8, 9, I0, which has a short time constant, to remove the high frequency components and leave the negative polarity direct current signals e, I which are applied to the grid of triode' l2. The plate of this triode is connected to ground through resistor l3 and its cathode is connected to the source of negative potential indicated at IS. A sliding contact l4 on resistor it, one end of which is grounded, couples the plate of tube l2 to the grid of tube IS. The cathode of this tube I is connected by an adjustable contact to a potentiometer l6 one end of which is connected to a. source of direct current and the other to ground. A capacitor I8 is connected between the plate and cathode of tube l2.

Resistors 20 and 2| in series are located be- ,tween the negative source of potential is and ground 25. Resistors 22 and 23 in series are located between a positive source of potential 24 and ground 25. A lead 28 extends from a point between resistors 20 and 2| to one end of resistor 21, the other end of which is grounded. The lead 28 extends from a point between resistors 22 and 23 to one end of resistor 16.

A sliding contact on resistor 21 is connected by lead 29 to the control grid 30 of a cathode ray tube T. The cathode 3| of this tube is connected through resistor 32 to ground and by lead 33 to the grid of triode l2.

The positive potential applied at 24 is coupled by lead 34 and connector 35 to the anode 36 of tube T, and by connector 31 to the focussing coil 38 of thistube T which is in turn connected by an adjustable resistor 38 to ground. The deflection coils 40 and 4| for the beam of the cathode ray tube T are connected in eries from lead 34 to the plate of tube l5.

The operation is as follows:

The signals consisting dashes and dots made up of say 5 kc. frequency oscillations as indicated at a. and b are applied to the primary l of the transformer. The output of the secondaries 2 and 2' of this transformer is applied alternately to the plates of tubes 3 and 4 and appears as rectified direct current signals with negative polarity modulated by 5 kc. frequency as shown at c, d. This output is filtered by filter 8lll to remove the high frequency components and yield the signals e, j which are applied to the grid of tube l2. The resistor l3 applies a positive voltage to the anode of tube l2 with respect to the negative voltage applied at l9 that is connected to its cathode, thus causing current to fiow from ground through resistor l3 and tube [2 to the negative terminal l9 during the time no signal is applied to the primary l of this transformer. The capacitor I8 is not charged appreciably during this time because the internal resistance of tube I2 is small compared to the high resistance at l3 when it is drawing current and therefore there is only a small potential at the plate of tube 12.

When the negative D. C. signal e, f is fed to the grid of tube l2 it cuts off the current through this tube, whereupon the capacitor l8 charges and yields the so-called A-shaped signals g, h which are applied at the desired potential by the gain control l3, l4 to the grid of tube l5. This causes amplified pulses of current of A-shape to pass through the horizontal deflecting coils 40, 4| from source 24 so that the beam og-tbe tube T is deflected comparatively slowly during the 2 a,soi,oaa

interval of time represented by the sloping line can be observed. Any suitable sort 0! speed conattheleftofthesignalsgandhandisreturned trolsuchasafoottypecanbeused-toalterthe almost instantly as represented by the very steep speed of rotation of the tube T. line at the right of these signals. This tube T What is claimed is: has the inside surface of its face coated in the s l. A telegraph code receiver, comprising a usual way with material which is rendered lunricathode-ray tube having a deflection system and nous wherever said beam strikes it. a surface upon which signals can be rendered The beam of the cathode ray tube T is devisible. means to cause code signals of high frecreased in intensity, except during the time when quency oscillations to become temporarily visible a signal is being applied to the grid of tube II, 1 upon said surface at different times. said means as follows: comprising an amplifying circuit tuned to said The lead 33 applies the rectangularly shaped oscillations and adjust d to yield rectans r 8 ssignals e, f to the cathode SI of tube '1 in negative nals, means to convert said rectangular signals polarity and the grid ll of this tube is biased into A-shapedsignals correspondinginamplitude negatively a sumcient amount by adimtment of 16 to the lengths of said rect n ular si na s. m ans the contactor on resistor 21 to decrease the into 8991! Bald heped signals to said deflection tensity of the beam of tube T when no signal is system, mean to cause said rectangular signals applied. when the negative signal 0, f voltage to turn on the ray of said cathode-raytube for is applied to the cathode Ii it biases this cathperiods of time in accordance with the lengths of ode Si in a negative direction to such an extent 90 said rectangular signals, and means to produce as to form the beam which is accelerated by anode I6 and strikes the screen of the tube '1 simmtaneously with the passing of current through the cells 40, 4|. Since pulses of current corresponding to dashes and dots pass through the deflecting cells 40, 4| simmtaneously with the longer and shorter intervals of time that the beam is turned on when the larger and smaller deflecting signals, respectively, are simultaneous- 1y applied to the coils, the signals are easily distinguished visually.

Provision may be made to rotate the tube T while the deflecting coils are kept stationary. The signals will then appear upon difierent locations on the screen surface of the tube. The tube can be rotated fast enough so that enough characters to make up several words within the are relative rotation between said cathode-ray tube and its beam.

2. The code receiver of claim 1, in which means are provided to cause said A-shaped signals are caused to produce temporary visible indications on different parts of said cathode-ray tube surface.

3. The device of claim 1, in which said first named means comprises a transformer.

4. The device of claim 1, in which said first named means comprises a transformer and a high frequency filter to filter out said high frequency oscillations.

5. The device of claim 1. in which an amplifier is provided for said A-shaped signals.

HAROLD EDWARD BESTE. 

